Monoclinic ZrO2 Phase Research Articles

CO induces the reduction of Mo in the glass liquid to molybdenum carbide to form glass defects in the hybrid furnace

In this work, a ceramic platinum continuous melting optical glass furnace containing oxygen combustion was taken as an example to analyze the causes of a unique glass defect. It was finally determined that the defect in the glass was composed of the top condensate, the brick skeleton, and the Mo2C generated in the glass liquid. It was determined that the monoclinic Al2O3 and ZrO2 phase in the brick desorbed the surface hydroxyl and water molecules under the high temperature environment inside the furnace, forming Lewis acid sites with the ability to adsorb electrons. CO was adsorbed on the surface of Al2O3 and ZrO2 by Lewis acid sites and fell into the glass liquid with the top condensate and the brick skeleton.CO then reduced Mo ions in the glass melt to form Mo2C, causing the formation of the defects in the glass.

Investigation of Structural Phase, Mechanical, and Tribological Characteristics of Layer Gradient Heat-Protective Coatings Obtained by the Detonation Spraying Method.

This paper presents the results of a study of layer gradient thermal protection coatings based on NiCrAlY and YSZ obtained by detonation spraying. Modern gas turbines and high-temperature units operate under extreme temperatures and aggressive environments, which requires effective protection of components from wear, corrosion, and thermal shocks. In this study, the use of layer gradient coatings consisting of alternating layers of NiCrAlY and YSZ was investigated with the aim of solving the problem of thermal stress accumulation due to a smooth change in the composition of the layers. Microstructural and phase analysis showed that alternating layers of NiCrAlY and YSZ formed a dense layer gradient structure with clear interphase boundaries and low porosity. Detonation spraying led to a complete transformation of the monoclinic ZrO2 phase into a tetragonal one, which significantly increased the mechanical strength of the coating and its resistance to thermal shocks. Sample 1D1 demonstrated excellent tribological and corrosion properties in a 3.5% NaCl solution, which can be explained by its higher density and reduced number of pores. Mechanical tests revealed stable values of hardness and wear resistance of the coating, especially for the 1D1 coating. Studies have shown that coatings are resistant to thermal shocks, but thicker layers show a tendency to peel off after thermal cycling. The obtained results indicate high prospects for the use of layer gradient coatings based on NiCrAlY and YSZ for the protection of gas turbine components and other high-temperature installations operating under extreme loads and aggressive environments.

Microstructure characterization of plasma electrolytic oxidation coating on Hf-Nb-Ta-Zr high entropy alloy

The morphology, composition, and microstructure of plasma electrolytic oxidation (PEO) coating on Hf-Nb-Ta-Zr high entropy alloy (HEA) were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, glow discharge optical emission spectroscopy (GDOES) and transmission electron microscopy (TEM). The formation mechanism of PEO coating was analyzed. It was found that a dense PEO coating of ∼4 μm thick on the HEA surface was formed, which consisted of tetragonal and monoclinic ZrO2 phases, tetragonal and monoclinic HfO2 phases, Nb2O5 and Ta2O5 phases. The PEO coating from the alloy substrate to the surface contained five distinctive layers: amorphous barrier layer, nanocrystalline layer, columnar grain layer, amorphous outer layer, and top porous layer. Their formation was ascribed to the different cooling rates of the melt in the different depths of the discharge channel across the coating. Meanwhile, the formation of an amorphous barrier layer near the HEA substrate was also related to the mutual migration and diffusion of Hf4+, Nb5+, Ta5+, Zr4+ and O2− besides the rapid cooling of melt in the bottom of the discharge channel. The columnar grains of ∼70 nm wide were mainly composed of the monoclinic ZrO2 and monoclinic HfO2 phases, but both the amorphous layers enrich the Ta and Nb elements. It was believed that the high-content Ta and Nb in the HEA enhanced the formation of the amorphous layers.

Thermally induced Modulation of optoelectronic characteristics In (ZrO2)0.8 doped (CuO) 0.2 screen printed thick films: An Innovative approach to enhanced materials

The Zirconium Dioxide (ZrO2) dopedCopper Oxide (CuO) thick films were fabricated on a glass substrate using the screen printing method, employing sintering temperatures of 500 °C, 550 °C, and 600 °C. The structural characteristics of the doped films were analyzed through Scanning Electron Microscopy (SEM), X-Ray Powder Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). Additionally, the optical properties were assessed via UV–Vis spectroscopy and Photoluminescence (PL) spectroscopy. SEM investigations revealed an increase in nanoparticle grain size and agglomeration as the sintering temperature was raised. XRD results exhibited the polycrystalline nature of the films and an augmented intensity of the monoclinic phase of ZrO2, with a noticeable preferred orientation along the (111) plane, which increased with higher sintering temperatures. FTIR analysis demonstrated slight peak shifts and increased sharpness as the sintering temperature was elevated. UV–Vis spectroscopy indicated a redshift in the reflectance edge, with the band gap transitioning from 3.81 eV (at 500 °C) to 3.65 eV (at 600 °C). These findings were corroborated by PL spectroscopy, which exhibited a redshift in the band emission as the sintering temperature increased. Electrical conductivity displayed semiconducting behavior of the sample. These investigations collectively indicate that elevating the sintering temperature leads to enhanced crystallinity in the films and a reduction in lattice deformations within the composite materials which is crucial for applications in large-area and flexible electronics.

Efficacy of mesoporous TiO2–ZrO2@g-C3N4 produced using a simple ultrasonic approach for copper ion removal from wastewater

The present study describes ultrasonically produced ternary composite material composed of carbon nitride nanosheets, zirconium, and titanium oxides for elimination of copper ions. The formation of monoclinic ZrO2, anatase TiO2, and g-C3N4 phases with respective crystallite sizes 6, 11, 13 nm were verified by the X-ray diffraction technique. The dispersion of the metal oxides nanoparticles with the graphitic nanosheets, the elemental composition of Zr, Ti, O, C and N, and the characteristic functional groups were verified respectively by TEM, EDX, and FTIR analysis that confirmed the successful formation and composition of the nanocomposite TiO2–ZrO2@g-C3N4 (TZCN). The good porosity of the composite that show a surface area, pore volume, and pore diameter values of 47.42 m2/g, 0.056 cm3 g−1, and 20.3 Å that nominate it for adsorption application. The adsorption capabilities of the nanocomposite were studied for copper ion removal from an aqueous solution, as well as the impacts of pH and starting Cu2+ concentration. The results show that the adsorption process is pH and starting concentration-dependent, with a maximum adsorption capacity of 447.8 mg/g. The Cu2+ adsorption is a monolayer chemisorption process that is well described by the Langmuir adsorption model and follows pseudo-second-order kinetics. Moreover, a plausible mechanism for Cu2+ ion adsorption on the surface of TZCN nanocomposite particles is proposed.

Effect of dopant loading and calcination conditions on structural and optical properties of ZrO2 nanopowders doped with copper and yttrium

Undoped, Cu and/or Y doped ZrO2 nanopowders were synthesized with Zr, Y, and Cu nitrates using a co-precipitation approach. Their structural and optical properties were examined regarding dopant content (0.1–8.0 mol.% of CuO and 3–15 mol.% of Y2O3) and calcination conditions (400 °C–1000 °C and, 1,2 or 5 h) through Raman scattering, XRD, TEM, EDS, AES, EPR, UV–vis and FTIR diffused reflectance methods. The results showed that both Cu and Y dopants promoted the appearance of additional oxygen vacancies in ZrO2 host, while the formation of tetragonal and cubic ZrO2 phases was primarily influenced by the Y content, regardless of Cu loading. The bandgap of most of the powders was observed within the 5.45–5.65 eV spectral range, while for those with high Y content it exceeded 5.8 eV. The (Cu,Y)-ZrO2 powders with 0.2 mol.% CuO and 3 mol.% Y2O3 calcined at 600 °C for 2 h demonstrated nanoscaled tetragonal grains (8–12 nm) and a significant surface area covered with dispersed CuxO species. For higher calcination temperatures, the formation of CuZr 2+ EPR centers, accompanied by tetragonal-to-monoclinic phase transformation, was found. For fitting of experimental FTIR reflection spectra, theoretical models with one, five, and seven oscillators were constructed for cubic, tetragonal, and monoclinic ZrO2 phases, respectively. Comparing experimental and theoretical spectra, the parameters of various phonons were determined. It was found that the distinct position of the high-frequency FTIR reflection minimum is a unique feature for each crystalline phase. It was centered at 700–720 cm−1, 790–800 cm−1, and 820–840 cm−1 for cubic, tetragonal, and monoclinic phases, respectively, showing minimal dependence on phonon damping coefficients. Based on the complementary nature of results obtained from structural and optical methods, an approach for monitoring powder properties and predicting catalytic activity can be proposed for ZrO2–based nanopowders.

Efficient Rhodamine B dye uptake onto MgZrO3@g-C3N4 nanostructures: Fabrication and adsorption mechanism

Pristine graphitic carbon nitride (g-C3N4) was synthesized by calcination of urea under elevated temperature. A blend of g-C3N4 nanosheets and nanosized ZrO2 and MgO precursors were used to prepare MgZrO3@g-C3N4 hybrid nanocomposite (MZCN) then it was assessed for the adsorption of Rhodamine B (RhB) dye from aqueous solution. The X-ray diffraction analysis revealed the development of the monoclinic ZrO2, cubic MgO, and hexagonal graphitic carbon nitride phases. The energy diffraction X-rays (EDX), photoelectron electron, and Fourier transformed infrared (FT-IR) spectroscopy analyses collectively validated the formation of the presumed composite. An improved porosity with a surface area 35.86 m2.g−1 and pore volume 0.087 cm3.g−1 were determined by N2 adsorption setup. The adsorption kinetics fitted well with the pseudo-first-order model (R2 > 0.99), which designated an adsorption process influenced by physisorption. The kinetics models investigations revealed a film diffusion control of the adsorption process. The adsorption equilibrium matched perfectly with the Langmuir isotherm model (R2 > 0.99) marking a maximum adsorption capacity of 370.8 mg g−1, demonstrating outstanding monolayer adsorption process. In addition, the Freundlich constant (n = 1.76) value is falling in the range 1–10 suggested a favorable adsorption of RhB onto the composite surface. The mechanistic enquiry suggested van der Waal, hydrogen bonds and π–π electron–donor interactions between the electron-rich RhB and the functional groups in the adsorbent’s molecule. This work stipulates that MgZrO3@g-C3N4 holds promise as efficient adsorbent for organic dyes from contaminated wastewater.

Co3O4-CuO-ZrO2 nanocomposite: Optical, spectral, morphological, structural and antibacterial studies

In this research, a tri-phase nanocomposite of Co3O4-CuO-ZrO2 was synthesized using the co-precipitation technique. The physical characteristics of the fabricated nanocomposites were analyzed through various analytical techniques including FTIR, XRD, SEM, EDX, and UV–visible spectroscopy. The XRD analysis underscored the formation of a nanocomposite consisting of cubic Co3O4, monoclinic ZrO2, and monoclinic CuO phases. The crystallite size (D) was determined using Scherrer's formula. Additionally, EDX analysis confirmed the intended elemental composition.The antibacterial activity results indicated a weak effect on both positive and negative bacteria. Furthermore, the energy bandgap of the Co3O4-CuO-ZrO2 nanocomposite was calculated to be 2.67 eV based on UV–visible spectroscopy. These findings suggest that the Co3O4-CuO-ZrO2 nanocomposite possesses exceptional properties, positioning it as a promising material for various optoelectronic applications.

Improvement of CMAS resistance of laser glazed and nano-modified YSZ thermal barrier coatings

The present investigation used atmospheric plasma spray (APS) as a method for the production of thermal barrier coatings composed of Yttria-stabilized zirconia (YSZ). A CO2 laser was used to remove surface cracks from the YSZ coatings' surface. Several parameter variations were applied to generate laser-glazed tracks on the coating surface, resulting in an impure surface microstructure with excellent surface properties. Scanning electron microscopy was utilized to analyse the tracks' microstructure. The optimal laser parameters were determined to be 77.7 W laser power, 215 mm laser distance, and, 120 mm s−1 scanning speed based on microstructural characteristics. Once the laser parameters had been optimized, a whole coating surface was laser glazed. In order to ascertain the impact of laser glazing, stability analysis, fracture toughness, and hardness evaluations were conducted on both unglazed and laser-glazed coatings. The growth of a network of cracks was seen on the surface. The surface roughness exhibited a reduction of about tenfold in comparison to the unglazed YSZ. The presence of the monoclinic ZrO2 phase within the coating structure was successfully eradicated. The laser glazing process resulted in enhancements to both the fracture toughness and surface hardness of the coating. Despite the fact that the gaps and imperfections on the coating surfaces were repaired during laser glazing, some cracked structures nonetheless appeared. Nano YSZ was deposited on laser-glazed surfaces by the electrophoretic method in order to eliminate cracks from laser-glazed surfaces. The experimental results obtained from conducting calcium-magnesium-alumina-silicate (CMAS) and hot corrosion tests on laser-glazed coatings indicate that the use of nano YSZ filler leads to a significant reduction in salt penetration during both glassy melt and hot corrosion processes.

Highly efficient ZrO2 photocatalysts in the presence of UV radiation synthesized in a very short time by plasma electrolytic oxidation of zirconium

We demonstrated in this paper that plasma electrolytic oxidation of zirconium in an alkaline electrolyte (10 g/L trisodium phosphate decahydrate) with the addition of NaAlO2 is a highly efficient method for obtaining ZrO2 coatings that are effective photocatalysts for the decomposition of organic pollutants under UV irradiation. ZrO2 coatings were formed by varying the PEO time from 60 s to 600 s, the NaAlO2 concentration up to 4 g/L, and characterized by SEM/EDS, XRD, XPS, DRS, and photoluminescence spectroscopy. Methyl orange decomposition was used to examine the photocatalytic activity (PA) of ZrO2 coatings. The PA of the formed PEO coatings is determined by the ratio of monoclinic and tetragonal ZrO2 phases, as well as the content of incorporated Al3+ in the crystal structure of ZrO2. Al3+ incorporated into ZrO2 coatings improves tetragonal phase stability by causing the formation of oxygen vacancies, which is crucial for enhancing their PA. Furthermore, the Al3+ dopant serves as a capture site for photo-induced electrons, inhibiting electron/hole recombination. The best PA was demonstrated by the ZrO2 coating formed after 60 s in an alkaline electrolyte with 4 g/L NaAlO2 addition, which contains the most tetragonal ZrO2 phases (around 51.3 %) and Al (around 3.14 at. %) of all formed ZrO2 coatings. After 8 h of irradiation, the PA of this coating was approximately 95 %.

Catalytic Oxidation of 1,2-Dichlorobenzene over Metal-Supported on ZrO2 Catalysts

The catalytic oxidation of environmentally unfriendly chlorinated organics is a powerful tool that can be used to completely mineralize these organic compounds. In this study, metals (Mn, Ni, V, and Fe) supported on zirconia have been investigated as catalysts in the oxidation of 1,2-dichlorobenzene. Metal supported on zirconia catalysts were prepared using the wet impregnation method. The catalyst materials were characterized by FT-IR, XRD, SEM–EDX, TEM, BET, and ICP methods. Metals were loaded on ZrO2 support at varied wt%, 2.5, 5, 7.5, and 10 which were confirmed by ICP-OES and EDX analysis. The XRD patterns of all the metals loaded on ZrO2 catalysts showed diffraction peaks that belong to the monoclinic phase of ZrO2 and few that are attributed to the oxides of the metals. The BET surface areas showed a significant decrease as the metal was loaded on ZrO2 support. The BET surface area of ZrO2 was 4.91 m2/g and when 2.5 and 7.5 wt% Fe was loaded on ZrO2 the BET surface areas were 4.48 and 3.09 m2/g, respectively. All the ozonation reactions of 1,2-dichlorobenzene were conducted in an impinger unit for 24 h. The aliquots were collected after 3, 6, 9, 12, 15, 18, and 24 of ozonation and analyzed using FT-IR and GC–MS analyses. The 7.5% Fe/ZrO2 was found to have a relatively high catalytic effect toward the conversion of 1,2-dichlorobenzene into mucochloric acid and 3,4-dichloro-2,5-furandione.

Gamma–radiation synthesis and characterization of nanocomposite hydrogels based on poly(vinyl-alcohol)/zirconium NPs/ europium

In the present work, nanocomposite hydrogels based on poly(vinyl-alcohol)/zirconium NPs/europium (PVA/ZrO2NPs/Eu3+) hybrid films were prepared by solution casting technique and then exposed to gamma irradiation (0–65 kGy). Zirconium oxide (ZrO2) nanoparticles (NPs) doped with 5mole% Eu3+ were prepared via sol gel technique. The polymer nanocomposite films were characterized by X-ray Diffraction (XRD) analysis, Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Furthermore, the PVA/ZrO2/Eu3+ nanocomposites were characterized for their optical properties using UV–Vis–NIR and photoluminescence (PL) spectroscopy. XRD analysis confirms the formation of ZrO2 monoclinic phase with the nanometer size (20 nm–11nm) when the γ-dose increases from 0 to 25 kGy respectively. Phase transition from monoclinic to tetragonal structure with an average particles size about 25 nm was observed when the γ-irradiation dose reaches 35 kGy. Increasing of γ-dose up to 65 kGy, a remarkable decrease in peaks intensity was observed and reappearance of the monoclinic ZrO2 phase again with average particle size about 10 nm. FTIR peaks intensity changes with increasing γ-irradiation doses. SEM observations showed that the nanocomposite film prepared at 35 kGy inhibits the agglomeration of ZrO2:Eu3+ nanoparticles in PVA host. The optical band gap energy decreases with increasing of γ-dose. PL measurements do not show any emission in the nanocomposite up to 25 kGy. However, at 35 kGy the sample exhibits characteristic orange-red emission centered at 607 nm attributed to 5D0→7F2 transition of Eu3+ ions. Further increasing of γ-dose up to 65 kGy, PL peaks intensity decreases drastically.

A Detailed Comparative Analysis of the Structural Stability and Electron-Phonon Properties of ZrO2: Mechanisms of Water Adsorption on t-ZrO2 (101) and t-YSZ (101) Surfaces.

In this study, we considered the structural stability, electronic properties, and phonon dispersion of the cubic (c-ZrO2), tetragonal (t-ZrO2), and monoclinic (m-ZrO2) phases of ZrO2. We found that the monoclinic phase of zirconium dioxide is the most stable among the three phases in terms of total energy, lowest enthalpy, highest entropy, and other thermodynamic properties. The smallest negative modes were found for m-ZrO2. Our analysis of the electronic properties showed that during the m-t phase transformation of ZrO2, the Fermi level first shifts by 0.125 eV toward higher energies, and then decreases by 0.08 eV in the t-c cross-section. The band gaps for c-ZrO2, t-ZrO2, and m-ZrO2 are 5.140 eV, 5.898 eV, and 5.288 eV, respectively. Calculations based on the analysis of the influence of doping 3.23, 6.67, 10.35, and 16.15 mol. %Y2O3 onto the m-ZrO2 structure showed that the enthalpy of m-YSZ decreases linearly, which accompanies the further stabilization of monoclinic ZrO2 and an increase in its defectiveness. A doping-induced and concentration-dependent phase transition in ZrO2 under the influence of Y2O3 was discovered, due to which the position of the Fermi level changes and the energy gap decreases. It has been established that the main contribution to the formation of the conduction band is made by the p-states of electrons, not only for pure systems, but also those doped with Y2O3. The t-ZrO2 (101) and t-YSZ (101) surface models were selected as optimal surfaces for water adsorption based on a comparison of their surface energies. An analysis of the mechanism of water adsorption on the surface of t-ZrO2 (101) and t-YSZ (101) showed that H2O on unstabilized t-ZrO2 (101) is adsorbed dissociatively with an energy of -1.22 eV, as well as by the method of molecular chemisorption with an energy of -0.69 eV and the formation of a hydrogen bond with a bond length of 1.01 Å. In the case of t-YSZ (101), water is molecularly adsorbed onto the surface with an energy of -1.84 eV. Dissociative adsorption of water occurs at an energy of -1.23 eV, near the yttrium atom. The results show that ab initio approaches are able to describe the mechanism of doping-induced phase transitions in (ZrO2+Y2O3)-like systems, based on which it can be assumed that DFT calculations can also flawlessly evaluate other physical and chemical properties of YSZ, which have not yet been studied quantum chemical research. The obtained results complement the database of research works carried out in the field of the application of biocompatible zirconium dioxide crystals and ceramics in green energy generation, and can be used in designing humidity-to-electricity converters and in creating solid oxide fuel cells based on ZrO2.

Direct conversion of carbon dioxide into light olefins over ZnZrOx/ZSM-5@n-ZrO2 tandem catalyst

The hydrogenation of carbon dioxide to light olefins is a direct and effective approach for achieving carbon neutrality. However, developing a tandem catalytic process involving methanol as an intermediate to achieve efficient directional conversion under mild conditions remains a challenge. Thus, we designed and constructed a bifunctional tandem catalyst, ZnZrOx/ZSM-5@n-ZrO2, where n represents the amorphous (am), monoclinic (m), and tetragonal (t) phases of ZrO2. The catalyst was prepared by coating an n-ZrO2 layer on the surface of ZSM-5 zeolite to form ZSM-5@n-ZrO2 with a coating structure, which was then ground and mixed with ZnZrOx to obtain the ZnZrOx/ZSM-5@n-ZrO2 tandem catalyst. At 340 °C and 2 MPa, the selectivity of the ZnZrOx/ZSM-5@t-ZrO2 catalyst toward light olefins reached 81.1%, with the carbon monoxide (CO) byproduct constituting only 34.3%. In contrast, the selectivity of ZnZrOx/ZSM-5 catalyst toward light olefins reached only 40.5% and a CO selectivity of 56.8%. Various characterizations and experimental results indicate that the ZSM-5@t-ZrO2 coating structure in the designed bifunctional catalyst effectively regulates the acid density and pore distribution of zeolite while inhibiting excessive hydrogenation of light olefins, ultimately achieving the desired mild transformation.

High energy devices and display technology applications of silver doped zirconium titanate nanoparticles

For the first of its kind, Silver activated (1–9 mol%) Zirconium Titanate nanoparticles (NPs) have been synthesized by green solution combustion method using AloeV era gel extract as a reducing agent followed by calcination at 720 °C for 3 h. All the synthesized samples crystallizes in orthorhombic crystal structure with the space group of Pbcn. Initially a less intense peak corresponding to monoclinic ZrO2 phase is observed up to 7 mol% and thereafter it diminishes at 9 mol%. The surface and bulk morphology were analyzed. The crystallite size increases whereas the direct energy band gap was found to decrease with increase in dopant concentration. Further, the effect of dopant concentration on photoluminescence and electrochemical properties were studied. The PL spectra show a single broad emission peak at 440 nm along with a satellite peak at 466 nm. These peaks appearing in the case of Ag-doped ZTO corresponds to the radiative transition of the excited electrons from occupied d bands to higher states of the Fermi level. The CIE and CCT coordinates imply that the present nanophosphor can be employed as a blue emitting phosphor material in display technology. The cyclic voltammetry analysis is performed for oxidation and redox peaks. EIS revealed the ion transport kinetics and Super capacitance values were obtained from GCD analysis. Specific capacitance values were found to be in the range 279 to 329 F/g for ZTO:Ag (1 to 9 mol%) NPs respectively. Thus, the present synthesized material might find applications in the field of display technology as well as in energy storage materials.

Effect of Pr doping on structure and luminescence properties of ZrO2 nanoparticles

Pr3+ impurity transitions in monoclinic and cubic phases of ZrO2 have been investigated by photoluminescence and thermoluminescence (TL). Zr(1−x)Pr x O2 (0 ⩽ x ⩽ 0.015) samples were prepared by the combustion method. Rietveld refined x-ray diffraction results confirm that undoped ZrO2 has a monoclinic structure, whereas Pr doped ZrO2 samples are in mixed phase consisting of monoclinic and cubic structures. ZrO2 shows a broad defect-related emission peak centered at 500 nm under an excitation wavelength of 300 nm. A series of Pr3+-related emissions are observed at 512, 584, 612–640 nm due to 3P0 → 3H4, 3P1 + 1I6 → 3H5, 1D2 → 3H4 transitions and between 719 and 740 nm due to 1D2 → 3H5 transitions when excited with 454 nm. The PL decay lifetime of Zr0.996Pr0.004O2 is 1.55 μs for fixed λ ex = 300 nm and λ em = 612 nm. The TL glow curve of Zr0.99Pr0.01O2 shows a prominent peak at 695 K and secondary peaks at 508 K and 570 K, which are not observed in undoped ZrO2. The TL emission measured at 695 K confirms that Pr3+ replaces Zr4+ in cubic lattice sites of ZrO2. This work shows the relationship between the luminescence properties and different structures of ZrO2 and that supports the design of new materials for possible applications.

Persistent luminescence of ZrO2:Tb3+ after beta particle irradiation for dosimetry applications

In this work, we report the Persistent Luminescence (PLUM) of ZrO2:Tb3+ samples synthesized by a conventional solid-state reaction and its performance in radiation dosimetry. X-ray diffraction shows the formation of the monoclinic phase of ZrO2 and the doping of the samples with Tb3+ ions and a mixture of Tb2O3. The ZrO2:Tb3+ 1% sample was exposed to beta particle irradiation in a dose range from 0.5 to 256 Gy. Immediately after removing the beta particle source, the PLUM response was measured for 600 s. The integrated area of the PLUM decay curves shows a sublinear dependence in the dose range from 0.5 to 64 Gy. The TL glow curve of the ZrO2:Tb3+ 1% sample showed two maxima at 79 and 150 °C after beta particle irradiation, suggesting that the trapping states associated with the maximum at 79 °C are responsible for the PLUM at room temperature. Computational deconvolution showed that the maximum at 79 °C consisted of two traps with first-order kinetics. The results suggest that the ZrO2:Tb3+ 1% sample has potential applications as a dosimeter for beta particle irradiation.

Evolution of morphology, microstructure and phase composition of zirconia thin coating on copper as a result of low energy high current pulsed electron beam irradiation

Using X-ray diffraction, scanning and transmission electron microscopy we studied the evolution of the morphology, microstructure and phase composition in the near-surface layer of copper covered with thin (2.8 μm) ZrO2 coating induced by low-energy high-current pulsed electron beam irradiation (the surface energy density was in the interval of 5.0–18.0 J/cm2, the accelerating voltage was 30 kV, the pulse duration was 3.2 μs, the number of pulses was 10). The variation of adhesion of the coating to substrate was evaluated using scratch testing. The evaporation of the upper part of the coating during irradiation was found and the thickness of the coating nonlinearly decreased with the increase of the energy density. We discussed the reasons for the surface cracking taking into account microstructural changes in the near-surface layer of the material. The irradiation was found to transfer most of monoclinic ZrO2 phase in the as-deposited coating to tetragonal and, possibly, cubic one. The factors influencing the adhesive strength of the coating were revealed and a potential for the increase of adhesion was demonstrated. We showed that irradiation with enhanced surface energy density was required to obtain copper-based composite hardened with zirconia nanoparticles in the near-surface layer. The thickness of the composite layer may be as much as 6 μm.

Thermophysical and mechanical properties of cubic, tetragonal and monoclinic ZrO2

Yttrium-stabilized zirconia (YSZ) materials are routinely used as thermal barrier coatings (TBCs). The phase composition and microstructure of YSZ materials significantly influence their properties. In this study, ZrO2 ceramics composed respectively of monoclinic ZrO2 (m-ZrO2), tetragonal YSZ (t-YSZ) and cubic YSZ (c-YSZ) phases were sintered. The effect mechanism of phase composition and microstructure on thermophysical and mechanical properties were investigated by experiment together and numerical calculation. The result indicates that YSZ materials with c-YSZ phase are more suitable as TBC materials in terms of heat insulation, thermal expansion match with the metal substrate, and strain tolerance. The YSZ ceramic with c-YSZ phase also exhibits lower thermal conductivity than those composed of the t-YSZ and m-ZrO2 phases due to its greater lattice distortion, number of oxygen vacancies, and lower sound velocity as a result of greater Y2O3 doping. Bond lengths and cohesive energy calculations based on first principles reveal that the reason that the Y2O3 doping causes the CTE values of ZrO2 to increase is due to the bonding between ions becoming weaker, and the c-YSZ phase exhibits the highest CTE value. First-principles calculations also indicate that the c-YSZ phase exhibits a lower elastic modulus and better malleability and plasticity than m-ZrO2 and t-YSZ phases. However, the t-YSZ phase has better fracture toughness due to toughening under stress and finer grains.

From doping to composites: zirconia (ZrO2) modified hematite photoanodes for water splitting.

Herein, a ZrO2 added α-Fe2O3 photoanode that can split water at low applied potential is reported. First, the pristine hematite α-Fe2O3 photoanode was synthesized using an aerosol-assisted chemical vapour deposition (AACVD) method followed by modification with various amounts of ZrO2 (2 to 40%) in the form of thin films on conducting glass substrate. The XRD, Raman spectroscopy and scanning electron microscopy (SEM) analyses confirmed the presence of the monoclinic phase of ZrO2 in the composites with multifaceted particles of compact morphology. The optical analysis showed an increase in the absorbance and variation in band gap of the composites ascribed to the heterogeneity of the material. The photoelectrochemical studies gave a photocurrent density of 1.23 mA cm-2 at 1.23 V vs. RHE for the pristine hematite and remarkably higher value of 3.06 mA cm-2 for the optimized amount of ZrO2 in the modified α-Fe2O3 photoanode. To the best of our knowledge, this is the highest photocurrent reported for a ZrO2 containing photoanode. The optimized composite electrode produced nine times more oxygen than that produced by pristine hematite.